The project aims at applying electron paramagnetic resonance (EPR) to probing structure and function of biological systems, and attempts to develop a new mode of application. Results of collaborative effort in 1988 include investigation of the mechanism of hemolysis induced by ultrasound (50 KHz) sonication; hemolysis was shown to be the result of physical damage due to shear stress attending sonication and not by the chemical insult of free radicals generated during sonication. The membrane fluidity, permeability, and deformability measured on the remaining erythrocytes after sonication are identical to the control suggesting that the cells that survived hemolysis have virtually no alterations in the structure due to sonication. The gamma radiolysis (700 Gy), on the other hand, was shown to cause significant damage to the structure of the surviving cells most likely as the result of free radical attacks. In our own project, the flow EPR technique devised in this laboratory for assessing erythrocyte deformability in flow was applied to studying the change of flow characteristics of resealed ghosts when the variables in ghost preparation are changed to investigate the rheological characteristics of membrane system itself apart from the influence by the cell contents. The ghost deformability in flow was found to improve that of the control ghost by the presence of Mg-ATP, chlorpromazine, or Ca2+ ions at the time of resealing, and by lysing the cell pseudo-isotonically in NH4HC03 solution with less osmotic stress than in ordinary hypotonic lysis. The improved ghost deformability was explained by the mechanism of recovery of natural balance in the bilayer system (including the cytoskeletal network) by these agents. Such balance is assumed to be perturbed during hypotonic lysis e.g. by transfer of inner layer phospholipids to the outer layer.